How many possible two letter combinations are there?

[gopunk]

ugh i can't believe i can't remember how to do this fifth grade stuff....

what i mean is like:

AA
AB
AC
.
.
.
.
ZX
ZY
ZZ


*every* combination... repetition doesn't matter, order does (ie, you can have both AB and BA).

also a nice explanation so i know how to do this in the future would be nice

thanks!

 

[glen]

26 x 26

 

[gopunk]

hmm.... that sure was simple...

thanks!

 

[glen]

GoPunk, you are smarter than I am.
I just got lucky.

 

[lukatmyshu]

The way you solve it is this ... for the first position you have 26 choices ..... That's why there at 26 possible one letter combinations (i.e. A,B,C) ...
multiply this by the number of choices you have for the second Letter (26) and you get 26*26 ....

 

[beer]

Wouldn't think be '26 choose 2'?

And isni't the infinite series for that like (N)(N-1)(N-2)...(N-(K+1)/K!?

 

[MiataGirl]

Originally posted by: Elemental007
Wouldn't think be '26 choose 2'?

And isni't the infinite series for that like (N)(N-1)(N-2)...(N-(K+1)/K!?

26 choose 2 would mean that order doesn't matter, and doesn't allow for repeats..i.e. AB is the same as BA...as it only means that you have a group of 26 things and wanted to pick 2. for example..if you had 26 students and wanted to pick 2 for something..26 choose 2 would give you how many combos of 2 kids are possible.

 

[Whitecloak]

Originally posted by: Elemental007
Wouldn't think be '26 choose 2'?

And isni't the infinite series for that like (N)(N-1)(N-2)...(N-(K+1)/K!?

it would be 26C2 if repetitions were not allowed.

 

[technogeeky]

repitions are not allowed.

It's not 26 * 26, its 26C2.

 

[beer]

SO wouldn't it be nPr then?

I haven't studied the series expansion for that though.
It's funny we're discussing this because I was tinkering around with the inf series sums of the binomial sereis earlier.

 

[glen]

repetition doesn't matter

 

[Whitecloak]

Originally posted by: Elemental007
SO wouldn't it be nPr then?

I haven't studied the series expansion for that though.
It's funny we're discussing this because I was tinkering around with the inf series sums of the binomial sereis earlier.

it would be nPr if order didnt matter

 

[Zebo]

26^2 permiatations, repition is not an issue cause ab does not equal ba. Glen knows.